1. Field of the Invention
The present invention relates to non-lead type resin-encapsulated semiconductor device referred to as QFN or DFN, and a method of manufacturing the same. In particular, the present invention relates to a resin-encapsulated semiconductor device including a lead terminal portion that is improved in mounting reliability, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, in order to respond to miniaturization of electronic equipment, high-density mounting of semiconductor components has been demanded. Along therewith, the semiconductor components are more miniaturized and thinned. As well as BGA and CSP packages, DFN and QFN type semiconductor devices are now in practical use as small-sized packages that use a lead frame.
FIG. 5A is a rearview of a related-art DFN package, and FIG. 5B is a cross-sectional view taken along the line A-A of FIG. 5A. In the DFN package, a plurality of lead portions 13 and a semiconductor element 11 mounted on a die pad portion 12 are encapsulated by an encapsulation resin 16, and the lead portions 13 and the die pad portion 12 are exposed from a rear surface of the package. The plurality of lead portions 13 are arrayed in two opposing directions on the rear surface of the package, and those lead portions form external leads. Further, the plurality of lead portions 13 are electrically connected to a surface electrode of the semiconductor element 11 via thin metal wires 14 inside the encapsulation resin 16.
In the DFN package, the plurality of lead portions 13 does not protrude outside from the resin 16, and hence the DFN package has an advantage in that the mounting area to a circuit board can be reduced. Further, by exposing the die pad portion 12 from the encapsulation resin 16, heat generated inside can be efficiently dissipated to the outside. Note that, there is another DFN package having a structure in which the die pad portion 12 is encapsulated inside the encapsulation resin 16. A QFN package has a structure in which external leads are exposed in four directions at the rear surface of the package.
FIG. 6 is a top view of a frame after resin encapsulation as viewed from above, followed by FIG. 7 as a cross-sectional view taken along the line B-B of the frame illustrated in FIG. 6. As illustrated in FIGS. 6 and 7, the following method has been adopted. That is, the semiconductor elements 11 mounted on the respective die pad portions 12 within the frame are encapsulated by the encapsulation resin 16, and then the encapsulation resin 16 and the lead portions 13 are simultaneously cut along cutting lines by a rotary blade of a dicing device. In this manner, as illustrated in FIG. 8, individual semiconductor devices are singulated (for example, see International Publication No. WO 99/67821 (FIG. 7)).
In this type of resin-encapsulated semiconductor device, the individual semiconductor devices are obtained by cutting positions of the lead portions 13 by the rotary blade after resin encapsulation and separating the semiconductor devices from the frame. However, the lead portions 13 are cut from the frame to be formed, and hence, as illustrated in FIG. 9, an end surface of a cut part of the lead portion 13 is not covered with a plating layer 17. When the semiconductor device is bonded to a circuit board 20 such as a printed board with use of solder 18, a solder fillet due to the solder 18 is not formed on a side surface part of the lead portion 13, which is exposed from the encapsulation resin portion. There is therefore a risk in that mounting strength weakens and mounting reliability lowers.
Mounting of the semiconductor device to the circuit board 20 is described with reference to the drawings. FIG. 9 is an enlarged view of an inside of a circle illustrated in FIG. 8, which illustrates the lead portion 13 of the semiconductor device. The plating layer 17, which is formed on other outer surfaces of the lead portion 13, is absent on an end surface part of the lead portion 13 that is subjected to lead cutting and is exposed from the encapsulation resin 16. Accordingly, a solder fillet is not formed on the end surface part of the lead portion 13 when the semiconductor device is mounted onto the circuit board 20 with a bonding agent such as the solder 18, as illustrated in FIG. 10 as a schematic cross-sectional view of the mounted state in an enlarged manner, which leads to reduction in mounting strength.
When a formation of a solder fillet on and over the end surface part of the lead portion 13 is necessary to gain a larger mounting strength, the end surface part and the upper surface portion of the lead portion 13 is protruded from the encapsulation resin 16, for example, as illustrated in FIG. 11 of an enlarged schematic cross-sectional view of the mounted state. The structure gives a larger mounting strength but the width between the right lead portion and left lead portion on the drawing becomes wider, decreasing the merit of a small package.